Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 240323
AFDMFR

Area Forecast Discussion
National Weather Service Medford OR
823 PM PDT SAT JUL 23 2016

.DISCUSSION...Patchy low clouds are expected again in the Coos Bay
area overnight but are not expected to cross the coastal range
into the Umpqua Basin. The strong North winds in the coastal
waters south of Cape Blanco came inside marine zone 356, and we
have updated the marine forecast to bring the Gale Warning to
include zone 356.

The 00Z NAM12 shows no major changes with warming Sunday into all
of next week as the upper level ridge builds into the area. The
atmosphere will be quite dry starting Tuesday and this will lead
to fire weather concerns, as we will also have offshore winds at
night for SW Oregon and western Siskiyou County. The ridge however
will keep moisture bottled up south of the Sacramento all of next
week, so no thunderstorms are in the forecast, not until next
Saturday at the earliest. /FB

&&

.AVIATION...24/00Z TAF cycle...Strong north winds will continue
along the Coos coast until around sunset, then they will diminish.
Stratus with MVFR CIGs may form along the Coos coast around dawn
tomorrow. Elsewhere, conditions will remain VFR through the current
TAF period. -Wright

&&

.MARINE...Updated 710 PM PDT Saturday 23 July 2016...A thermal
trough along the coast and high pressure offshore will produce
strong north winds and wind driven seas over the waters through at
least the end of next week. Gales are certain over the waters south
of Cape Blanco beyond roughly 5 NM from shore with small craft
advisory level conditions elsewhere.

On Tuesday, surface pressure gradients tighten considerably, and
winds just above the surface increase to as much as 50 kt. As a
result, the area of gales expands, and there may be a small area
over the southern outer waters where winds approach storm force.
This also the most likely time when gales could affect a small
part of the northern zones as well. -Wright

&&

.PREV DISCUSSION... /Issued 717 PM PDT SAT JUL 23 2016/

UPDATE...Based on latest observations and model data, the marine
forecast was updated to expand the Gale warning into the southern
inner waters. Buoy 27 is showing gales currently, and the guidance
that captured this best (HiRes NMM) shows this occurring again
tomorrow and Monday. See the updated marine discussion below for
further details. -Wright

MARINE...Updated 710 PM PDT Saturday 23 July 2016...A thermal
trough along the coast and high pressure offshore will produce
strong north winds and wind driven seas over the waters through at
least the end of next week. Gales are certain over the waters
south of Cape Blanco beyond roughly 5 NM from shore with small
craft advisory level conditions elsewhere.

On Tuesday, surface pressure gradients tighten considerably,
and winds just above the surface increase to as much as 50 kt. As
a result, the area of gales expands, and there may be a small
area over the southern outer waters where winds approach storm
force. This also the most likely time when gales could affect a
small part of the northern zones as well. -Wright

PREV DISCUSSION... /Issued 446 PM PDT SAT JUL 23 2016/

AVIATION...24/00Z TAF cycle...Strong north winds will continue
along the Coos coast until around sunset, then they will diminish.
Stratus with MVFR CIGs may form along the Coos coast around dawn
tomorrow. Elsewhere, conditions will remain VFR through the current
TAF period. -Wright

PREV DISCUSSION... /Issued 345 PM PDT SAT JUL 23 2016/

Updated fire weather discussion.

DISCUSSION...23/12Z NAM/GFS/EC in.

Mostly clear skies this afternoon over the Medford CWA...except
for some marine stratus well offshore.

Flow aloft remains nearly westerly this afternoon. The upper
level pattern will alternate between weak zonal flow and weak
troughing through Wednesday...with little in the way of short wave
activity over our area. The ridges of the coast range will be dry
and breezy during the overnight hours due to low to moderate...but
persistent...easterly low level flow. Stronger winds have returned
to the coastal waters due to the strengthening thermal trough.

Temperatures will warm through Monday. Highs in the Umpqua Basin
will warm to near normal values by Sunday...and inland highs over
the remainder of the area will warm to 5 to 10 degrees above
normal. High temperatures will warm around 5 degrees or so over
the west side and northern California Monday through
Wednesday...but only a degree or two over the east side during
that stretch.

Upper level ridging will build in more strongly Wednesday into
Thursday...bringing hotter temperatures to the area. Inland highs
Thursday will warm to 5 to 10 degrees above normal over Oregon and
10 to 15 degrees above normal over northern California.

The ridge will begin to weaken Thursday into Friday as short waves
embedded in the westerly flow move through...but inland
temperatures will keep on warming through at least Friday...when
the highs will be 10 to 15 degrees above normal.

The ridge will weaken further Saturday as more short waves move
through. Inland temperatures will cool a few degrees. The 23/12Z
EC is advertising dry conditions for that day while the 23/12Z
GFS model run indicates the possibility of afternoon and evening
thunderstorms...which is consistent with the GFS/EC 22/12Z
solutions. Therefore...have added afternoon/evening thunderstorms
to the forecast for next Saturday...but there is still a lot of
uncertainty this far out.

FIRE WEATHER...Updated 300 PM PDT Saturday 23 July 2016. It will
be hot and dry through the next week. Breezy north winds are
expected west of the Cascades today and tomorrow while East Side
winds will be relatively light with typical afternoon breezes. A
Haines Index of 6...indicating very dry and unstable
conditions...is expected east of the Cascades. Areas west of the
Cascades will feature a Haines Index value of 5, with more stable
conditions compared to the East Side. A long-duration surface
thermal trough will bring periods of breezy northeast overnight
winds and moderate humidity recoveries through Thursday at the
coast and in Western Siskiyou County. Moderate humidity recoveries
are also expected east of the Cascades through Thursday. Lastly,
weak instability may develop on Saturday, and a slight chance of
thunderstorms has been introduced into the forecast. /DW

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.

CA...None.

Pacific Coastal Waters...Small Craft Advisory until 11 PM PDT Friday for
     PZZ350-356-370-376.
     Gale Warning until 11 PM PDT Friday for PZZ356-376.

$$

FJB/JRS/TRW



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